In drilling a well, a drill string is used. The drill string can comprise a drill bit attached to sections of drill pipe. As the well is drilled, additional sections of drill pipe are added to the drill string to extend its length until the well is drilled deep enough to reach a formation where substances, such as water, oil or gas, can be produced from the well. Sections of pipe are joined together using threaded connections on the pipe, often referred to as “pin” and “box”, where the pin of one section of pipe is threaded into the box into an adjoining section of pipe. The drill string is rotated to turn the drill bit in order to drill the well. When the drill string is removed from the wellbore, the sections of pipe can be removed from the drill string one or more sections at a time.
To make or break the threaded connection between sections of pipe, a power tong device can be used to do so. Known designs use a motor with a transmission to operate the power tong mechanism to grip and turn one section of pipe relative to another section of pipe to thread them together or to separate them. When breaking a joint, the power tong uses a lower gear to increase the torque applied to the pipe to a level required to break the joint, then the power tong is shifted to a higher gear to increase the rotation speed of the pipe to unthread the connection. When a making a joint, the higher gear can be used to start the threaded connection, and then the lower gear is used to torque the connection together. This process of shifting gears to make or break joints is time consuming, and can make the time required to replace a worn out drill bit, thus requiring the complete removal of the entire drill string and then reinstalling the drill string, quite lengthy.
It is, therefore, desirable to provide a power tong overcomes the shortcomings of the prior art and decrease the time required to make and break joints between sections of pipe on a drilling rig.